Liquid crystalline medium

ABSTRACT

The present invention relates to a liquid-crystalline medium based on a mixture of polar compounds having negative dielectric anisotropy (Δ∈), which is distinguished by the fact that it has a value for the ratio γ 1 /Δn 2  in the range 6-45 with a clearing point of &gt;60° C. and a Δ∈ of ≦−2.3. Media of this type are particularly suitable for electro-optical displays having active-matrix addressing based on the ECB, PA LCD, FFS or IPS effect.

The present invention relates to a liquid-crystalline medium and to theuse thereof in liquid-crystal displays, in particular liquid-crystaldisplays addressed by means of an active matrix (AMDs or AMLCDs foractive matrix addressed liquid crystal displays). Particular preferenceis given to displays which use an active matrix comprising thin-filmtransistors (TFTs) or varistors. AMDs of this type can use variousactive electronic switching elements. The most widespread are displayswhich use three-pole switching elements. Examples of three-poleswitching elements of this type are MOS (metal oxide silicon)transistors or the above-mentioned TFTs or varistors. Varioussemiconductor materials, predominantly silicon, or also cadmiumselenide, are used in the TFTs. In particular, polycrystalline siliconor amorphous silicon is used. In contrast to the three-pole electronicswitching elements, matrices of two-pole switching elements, such as,for example, MIM (metal insulator metal) diodes, ring diodes orback-to-back diodes, can also be employed in AMDs.

In liquid-crystal displays of this type, the liquid crystals are used asdielectrics whose optical properties change reversibly on application ofan electrical voltage. Electro-optical displays which use liquidcrystals as media are known to the person skilled in the art. Theseliquid-crystal displays use various electro-optical effects.

The most widespread conventional displays use the TN effect (twistednematic, having a nematic structure twisted by about 90°), the STNeffect (supertwisted nematic) or the SBE effect (supertwistedbirefringence effect). In these and similar electro-optical effects,liquid-crystalline media having positive dielectric anisotropy (Δ∈) areused.

In contrast to the said conventional displays, which requireliquid-crystal media having positive dielectric anisotropy, there areother electro-optical effects which use liquid-crystal media havingnegative dielectric anisotropy, such as, for example, the ECB effect(electrically controlled birefringence) and its subforms DAP(deformation of aligned phases), VAN (vertically aligned nematics), MVA(multidomain vertical alignment), ASV (advanced super view), PVA(patterned vertical alignment) and CSH (colour super homeotropics).

The principle of electrically controlled birefringence, the ECB effect(electrically controlled birefringence) or also DAP effect (deformationof aligned phases), was described for the first time in 1971 (M. F.Schieckel and K. Fahrenschon, “Deformation of nematic liquid crystalswith vertical orientation in electrical fields”, Appl. Phys. Left. 19(1971), 3912). This was followed by papers by J. F. Kahn (Appl. Phys.Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44(1973), 4869).

The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers(1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82Digest Techn. Papers (1982), 244) have shown that liquid-crystallinephases must have high values for the ratio of the elastic constantsK₃/K₁, high values for the optical anisotropy Δn and values for thedielectric anisotropy Δ∈ of −0.5 to −5 in order to be usable forhigh-information display elements based on the ECB effect.Electro-optical display elements based on the ECB effect have ahomeotropic edge alignment.

The IPS effect (in plane switching) increasingly employed recently canuse both dielectrically positive and also dielectrically negativeliquid-crystal media, similarly to “guest/host” displays, which canemploy dyes, depending on the display mode used, either indielectrically positive or in dielectrically negative media. A furtherhighly promising type of liquid-crystal displays are so-called “axiallysymmetric microdomain” (ASM for short) displays, which are preferablyaddressed by means of plasma arrays (PA LCDs from “plasma addressedliquid crystal displays”).

The liquid-crystal media employed in the above-mentioned liquid-crystaldisplays and in all liquid-crystal displays utilising similar effectsgenerally comprise liquid-crystal compounds having the correspondingdielectric anisotropy, i.e. comprising compounds having positivedielectric anisotropy in the case of dielectrically positive media andcomprising compounds having negative dielectric anisotropy in the caseof dielectrically negative media.

The liquid-crystal media of the prior art generally have relatively lowbirefringence values, relatively high operating voltages (the thresholdvoltages (V₀) are often relatively high, in some cases greater than 2.3V) and relatively long response times, which are inadequate, inparticular, for video-capable displays. Furthermore, they are usuallyunsuitable for high operating temperatures and/or have inadequatelow-temperature stabilities (LTSs). Thus, for example, the nematicphases often only extend down to −20° C. and in some cases even onlydown to −10° C.

For the most part, the liquid-crystal media of the prior art haverelatively unfavourable values for Δn, which are often significantlysmaller than 0.11 and in some cases smaller than 0.10. However, suchsmall Δn values are not particularly advantageous, for example, for VANdisplays, since they require the use of cells having relatively largelayer thicknesses, of 4 μm or more, and thus result in response timeswhich are unacceptably long for many applications. Thus, a d·Δn ofapproximately 0.30 μm is employed in the case of an untwisted directoralignment.

However, the use of cells having very small layer thicknesses frequentlyresults in low production yields in the displays. For fast-switchingdisplays, Δn values in the range from 0.075 to 0.15 are preferablydesired. This applies both in the case of ECB displays and also in thecase of IPS displays.

Since the response times of the prior art displays, as already mentionedabove, are often too long, the viscosities of the liquid-crystal mediamust be improved and thus reduced. This applies, in particular, to therotational viscosity γ₁ and very particularly to the value thereof atlow temperatures. A reduction in the flow viscosity ν₂₀ generallyresults, in particular in the case of displays having a homeotropic edgealignment of the liquid crystals (for example in the case of ECB and VANdisplays), in a very desired shortening of the response times.

For industrial use of this effect in electro-optical display elements,there is a requirement for LC phases which have to satisfy amultiplicity of requirements. Particularly important here are thechemical resistance to moisture, air and physical influences, such asheat, radiation in the infrared, visible and ultraviolet regions, anddirect and alternating electric fields.

Furthermore, LC phases which can be used industrially are required tohave a liquid-crystalline mesophase in a suitable temperature range andlow viscosities.

None of the series of compounds having a liquid-crystalline mesophasethat are known to date includes a single compound which meets all theserequirements. In general, therefore, mixtures of from two to 25,preferably from three to 18, compounds are prepared in order to obtainsubstances which can be used as LC phases. However, it has not beenpossible to prepare optimum phases easily in this way, since noliquid-crystal materials having significantly negative dielectricanisotropy and adequate long-term stability were hitherto available.

The displays based on the ECB effect and optionally on the IPS or PALCDeffect have to date required specific, complex matching of theliquid-crystal mixtures to be employed to the particular mode or theparticular configuration, in particular concerning Δn and Δ∈ values andthe rotational and flow viscosities.

Surprisingly, it has now been found that liquid-crystalline mixtureshaving negative anisotropy which have a certain ratio of γ₁ and Δn orthe square thereof do not have the disadvantages of the media from theprior art, or at least only do so to a significantly reduced extent. Thepresent mixture concept according to the invention enables negativemixtures which can be employed universally for the ECB effect to beconceived easily for the various modes. The mixtures according to theinvention are particularly suitable for VAN displays in the MVA and PVAconfigurations, furthermore for IPS, FFS and PA LCD.

The present invention thus relates to a liquid-crystalline medium basedon a mixture of polar compounds having negative dielectric anisotropy(Δ∈), which is distinguished by the fact that it has a value for theratio γ₁/Δn² in the range 6-45 Pa·s with a clearing point of >60° C. anda Δ∈ of ≦−2.3.

All values for the ratio of γ₁/Δn² indicated in this application havethe unit [Pa·s], unless stated otherwise.

The mixtures according to the invention are distinguished by their shortresponse times in ECB displays, a broad nematic phase and relativelyhigh values for the voltage holding ratio (HR). The mixtures accordingto the invention having a γ₁/Δn² ratio of this type furthermore exhibitvery favourable values for the capacitive threshold and at the same timevery good low-temperature stability.

The invention therefore also relates to the use of theliquid-crystalline mixtures, in particular for displays based on theECB, PALCD and IPS effect, and to the corresponding displays containingthe mixtures according to the invention.

Preferred embodiments of the mixture concept according to the inventionare indicated below.

The mixtures according to the invention preferably have a γ₁/Δn² of6-30, preferably of 6-22.

The values for the optical anisotropy Δn are preferably in the range0.08-0.12. Particular preference is given to mixtures having aΔn=0.08±0.01, furthermore having a Δn=0.10±0.005 and Δn=0.12±0.01.

The mixtures according to the invention preferably have clearing pointsof ≧65° C., in particular of ≧69° C.

The thresholds V₀ (capacitive) are preferably in the range 1.8-2.3 V.

The temperature stability (LTS) is preferably at least 1000 h attemperatures of ≦−20° C., in particular ≦−30° C. and very particularlypreferably ≦−40° C.

Mixtures which satisfy the required ratio of γ₁/Δn² preferably have,depending on Δn, Δ∈ and the clearing point, the following rotationalviscosities, as tabulated below:

1. Clearing point 70° C.±5° C. and Δ∈ of −3.0±0.6

Δn Rotational viscosities γ₁ 0.08 ± 0.005 ≦125 mPa · s, preferably ≦105mPa · s 0.09 ± 0.005 ≦130 mPa · s, preferably ≦105 mPa · s 0.10 ± 0.005≦135 mPa · s, preferably ≦110 mPa · s 0.11 ± 0.005 ≦145 mPa · s,preferably ≦120 mPa · s 0.12 ± 0.005 ≦150 mPa · s, preferably ≦125 mPa ·s 0.13 ± 0.005 ≦160 mPa · s, preferably ≦135 mPa · s 0.15 ± 0.01  ≦170mPa · s, preferably ≦145 mPa · s

-   -   The value for the ratio of γ₁/Δn² is preferably in the range        8.6-18.5. The thresholds are preferably <2.3 V, in particular in        the range 2.0-2.3 V.        2. Clearing point 70° C.±5° C. and Δ∈ of −4.0±0.4

Δn Rotational viscosities γ₁ 0.08 ± 0.005 ≦140 mPa · s, preferably ≦120mPa · s 0.09 ± 0.005 ≦165 mPa · s, preferably ≦145 mPa · s 0.10 ± 0.005≦185 mPa · s, preferably ≦150 mPa · s 0.11 ± 0.005 ≦190 mPa · s,preferably ≦160 mPa · s 0.12 ± 0.005 ≦195 mPa · s, preferably ≦175 mPa ·s 0.13 ± 0.005 ≦205 mPa · s, preferably ≦180 mPa · s 0.15 ± 0.01  ≦220mPa · s, preferably ≦185 mPa · s

-   -   The value for the ratio of γ₁/Δn² is preferably in the range        9.5-20.0. The thresholds are preferably <2.1 V, in particular in        the range 1.8-2.1 V.        3. Clearing point 70° C.±5° C. and Δ∈ of −5.0±0.6

Δn Rotational viscosities γ₁ 0.08 ± 0.005 ≦185 mPa · s, preferably ≦175mPa · s 0.09 ± 0.005 ≦200 mPa · s, preferably ≦165 mPa · s 0.10 ± 0.005≦210 mPa · s, preferably ≦165 mPa · s 0.11 ± 0.005 ≦220 mPa · s,preferably ≦190 mPa · s 0.12 ± 0.005 ≦230 mPa · s, preferably ≦200 mPa ·s 0.13 ± 0.005 ≦250 mPa · s, preferably ≦210 mPa · s 0.15 ± 0.01  ≦270mPa · s, preferably ≦220 mPa · s

-   -   The value for the ratio of γ₁/Δn² is preferably in the range        12.0-22.0. In the case of Δ∈ values of 0.08±0.005, the value may        also be in the range 26-28. The thresholds are preferably <1.9        V, in particular in the range 1.7-1.8 V.        4. Clearing point 90° C.±5° C. and Δ∈ of −3.0±0.6

Δn Rotational viscosities γ₁ 0.08 ± 0.005 ≦160 mPa · s, preferably ≦130mPa · s 0.09 ± 0.005 ≦170 mPa · s, preferably ≦135 mPa · s 0.10 ± 0.005≦180 mPa · s, preferably ≦140 mPa · s 0.11 ± 0.005 ≦190 mPa · s,preferably ≦150 mPa · s 0.12 ± 0.005 ≦200 mPa · s, preferably ≦190 mPa ·s 0.13 ± 0.005 ≦210 mPa · s, preferably ≦195 mPa · s 0.15 ± 0.01  ≦220mPa · s, preferably ≦200 mPa · s

-   -   The value for the ratio of γ₁/Δn² is preferably in the range        12.0-23.0. The thresholds are preferably <2.6 V, in particular        in the range 2.30-2.55 V.        5. Clearing point 90° C.±5° C. and Δ∈ of −4.0±0.4

Δn Rotational viscosities γ₁ 0.08 ± 0.005 ≦185 mPa · s, preferably ≦150mPa · s 0.09 ± 0.005 ≦195 mPa · s, preferably ≦160 mPa · s 0.10 ± 0.005≦215 mPa · s, preferably ≦200 mPa · s 0.11 ± 0.005 ≦215 mPa · s,preferably ≦190 mPa · s 0.12 ± 0.005 ≦215 mPa · s, preferably ≦200 mPa ·s 0.13 ± 0.005 ≦235 mPa · s, preferably ≦210 mPa · s 0.15 ± 0.01  ≦250mPa · s, preferably ≦210 mPa · s

-   -   The value for the ratio of γ₁/Δn² is preferably in the range        14.5-22.0. The thresholds are preferably <2.25 V, in particular        in the range 2.00-2.25 V.        6. Clearing point 90° C.±5° C. and Δ∈ of −5.0±0.6

Δn Rotational viscosities γ₁ 0.08 ± 0.005 ≦280 mPa · s, preferably ≦265mPa · s 0.09 ± 0.005 ≦275 mPa · s, preferably ≦260 mPa · s 0.10 ± 0.005≦275 mPa · s, preferably ≦260 mPa · s 0.11 ± 0.005 ≦275 mPa · s,preferably ≦265 mPa · s 0.12 ± 0.005 ≦280 mPa · s, preferably ≦265 mPa ·s

-   -   The value for the ratio of γ₁/Δn² is preferably in the range        18.0-25.0. In the case of Δ∈ values of 0.08±0.005, the value may        also be in the range 40-45. The thresholds are preferably <2.0        V, in particular in the range 1.8-2.0 V.

Mixtures according to the invention having clearing points of 75-85° C.each have γ₁/Δn² values and γ₁ values between the above-mentioned limitsfor 70±5° C. and 90±5° C.

Preferred embodiments of the mixtures according to the invention withrespect to their composition are mentioned below:

-   a) Liquid-crystalline medium which comprises at least two compounds    of the formulae IA, IB and/or II

-   -   in which    -   R¹ and R² each, independently of one another, denote H, an alkyl        or alkenyl radical having up to 15 C atoms which is        unsubstituted, monosubstituted by CN or CF₃ or at least        monosubstituted by halogen, where, in addition, one or more CH₂        groups in these radicals may be replaced by —O—, —S—,

-   -    —C≡C—, —OCF₂—, —CF₂O—, —OC—O— or —O—CO— in such a way that O        atoms are not linked directly to one another, and    -   v denotes 1 to 6.    -   R¹ and R² preferably denote straight-chain alkyl or        straight-chain alkenyl.    -   Preferred mixtures, in particular having an n value of        0.08-0.09, comprise in total four compounds of the formulae

-   b) Liquid-crystalline medium which additionally comprises one or    more compounds of the formula III

-   -   in which    -   R³¹ and R³² each, independently of one another, denote a        straight-chain alkyl, alkylalkoxy or alkoxy radical having up to        12 C atoms, and

-   -    denotes

-   -    and    -   Z denotes a single bond, —C₂H₄—, —CH═CH—, —(CH₂)₄—, —(CH₂)₃O—,        —O(CH₂)₃—, —CH═CHCH₂CH₂—, —CH₂CH₂CH═CH—, —CH₂O—, —OCH₂—, —CF₂O—,        —OCF₂—, —COO—, —OCO—, —C₂F₄—, —CHFCF₂—, —CF═CF—, —CH═CF—,        —CF═CH—, —CH₂—.    -   The mixtures according to the invention may comprise up to 50%        by weight of neutral compounds, preferably selected from the        compounds of the formula

-   c) Liquid-crystalline medium which comprises four, five, six or    more, preferably two or three, compounds of the formulae IA and/or    IB.

-   d) Liquid-crystalline medium in which R¹ and R² in the formulae IA    and IB preferably have the following meanings: straight-chain alkyl,    vinyl, 1E-alkenyl or 3-alkenyl.    -   If R¹ and/or R² denote alkenyl, it is preferably CH₂═CH,        CH₃—CH═CH, C₃H₇—CH═CH, CH₂═CH—C₂H₄ or CH₃—CH═CH—C₂H₄.    -   In the compounds IA, IB and II, v preferably denotes 2, 3 or 4.

-   e) Liquid-crystalline medium in which the proportion of compounds of    the formulae IA and/or IB in the mixture as a whole is at least 10%    by weight, preferably at least 25% by weight and very particularly    preferably ≧30% by weight.

-   f) Liquid-crystalline medium in which the proportion of compounds of    the formula II in the mixture as a whole is at least 10% by weight.

-   g) Liquid-crystalline medium comprising at least two, preferably    three, compounds of the formula II, in particular of the formula

-   -   R² preferably denotes ethyl, propyl or pentyl.

-   h) Liquid-crystalline medium in which the proportion of compounds of    the formula III in the mixture as a whole is at least 5% by weight.

-   i) Liquid-crystalline medium which additionally comprises a compound    selected from the formulae IIIa to IIIj:

-   -   in which    -   alkyl and alkyl* each, independently of one another, denote a        straight-chain alkyl radical having 1-6 C atoms, and    -   alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms, preferably        vinyl, 1E-alkenyl or 3E-alkenyl.    -   The medium according to the invention preferably comprises at        least one compound of the formula IIIa, formula IIIb and/or        formula IIIe, preferably in amounts of >5% by weight, in        particular >10% by weight, very particularly preferably >20% by        weight.    -   Particularly preferred compounds of the formulae IIIe and IIIf        are mentioned below:

-   j) Liquid-crystalline medium which comprises at least three    compounds of the formula IIIe, preferably selected from the group of    the compounds

-   -   The proportion of the compounds IIIe-1, IIIe-2 and/or IIIe-3 in        the mixture, preferably having a Δn=0.08 (±0.005), is preferably        ≧20% by weight, in particular ≧30% by weight. alkyl preferably        denotes C_(n)H_(2n+1), where n=3, 4 or 5.    -   Preference is furthermore given to media which comprise the        compound of the formula

-   -   preferably in concentrations >20% by weight, in particular >30%        by weight, preferably in combination with the compound of the        formula

-   -   The latter compounds are preferably present in the mixture in        amounts of 5-40% by weight.

-   k) Liquid-crystalline medium which essentially consists of:    -   10-40% by weight of one or more compounds of the formulae IA and        IB, and    -   10-40% by weight of one or more compounds of the formula II.

-   l) Liquid-crystalline medium which additionally comprises one or    more tetracyclic compounds of the formulae

-   -   in which    -   R⁷ and R⁸ each, independently of one another, have one of the        meanings indicated for R¹ in Claim 1, and    -   w and x each, independently of one another, denote 1 to 6.

-   m) Particularly preferred media comprise one or more indane    compounds selected from the group of the compounds of the formulae    In-a to In-d:

-   -   in which    -   alkyl and alkyl* each, independently of one another, denote a        straight-chain alkyl radical having 1-6 C atoms, and    -   alkenyl denotes a straight-chain alkenyl radical having 2-6 C        atoms,    -   alkyl* preferably denotes CH₃, C₂H₅ or n-C₃H₇.    -   The mixtures according to the invention preferably comprise a        compound of the formula In-a or In-b, in particular a compound        of the formula In-a. The proportion of the indane compounds in        the mixture as a whole is at least 5% by weight, preferably at        least 10% by weight.

-   n) Liquid-crystalline medium which additionally comprises one or    more compounds of the formulae

-   -   in which R¹³-R²⁷ each, independently of one another, have the        meanings indicated for R¹, and z and m each, independently of        one another, denote 1-6. R^(E) denotes H, CH₃, C₂H₅ or n-C₃H₇,        and x denotes 0, 1, 2 or 3.    -   The said compounds are preferably each present in the mixture as        a whole in amounts of at least 5% by weight.    -   Mixtures having a Δn in the range 0.08-0.12 preferably comprise        compounds of the formula

-   -   in concentrations of ≧5% by weight, preferably 10% by weight.    -   Mixtures of this type furthermore comprise compounds of the        formula II in amounts of ≧2% by weight.    -   The compounds of the formula

-   -   are particularly suitable for mixtures having a Δ∈ value in the        range 0.07-0.10, in particular 0.07-0.09. These compounds, in        which R²⁷ preferably denotes alkyl, are preferably employed in        concentrations of 5-20% by weight.

-   o) Liquid-crystalline medium additionally comprising one or more    fluorinated terphenyls of the formulae T-1 to T-22

-   -   in which    -   R has the meanings indicated for R¹.    -   R is preferably straight-chain alkyl, alkoxy or alkylalkoxy,        each having 1-6 C atoms, alkenyl or alkenyloxy having 2-6 C        atoms. R preferably denotes methyl, ethyl, propyl, butyl,        pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy.    -   The medium according to the invention preferably comprises the        terphenyls of the formulae T-1 to T-22 in amounts of 2-30% by        weight, in particular of 5-20% by weight.    -   Particular preference is given to compounds of the formulae T-1,        T-2, T-3 and T-22. In these compounds, R preferably denotes        alkyl, furthermore alkoxy, each having 1-5 C atoms.    -   The terphenyls are preferably employed in mixtures having a        Δn≧0.10 in combination with the compounds of the formulae IA, IB        and II. Preferred mixtures comprise 2-20% by weight of        terphenyls and 5-30% by weight of the compounds of the formula

-   p) Liquid-crystalline medium additionally comprising one or more    biphenyls of the formulae B-1 to B-4

-   -   in which alkyl, alkyl*, alkenyl and alkenyl* have the        above-mentioned meanings.    -   The proportion of the biphenyls of the formulae B-1 to B-4 in        the mixture as a whole is preferably at least 3% by weight, in        particular ≧5% by weight.    -   Of the compounds of the formulae B-1 to B-4, the compounds of        the formulae B-1 and B-4 are particularly preferred.    -   Preferred biphenyls are likewise

-   q) Liquid-crystalline medium additionally comprising one or more    esters of the formulae E-1 to E-3

-   -   in which alkyl and alkyl* have the above-mentioned meanings.    -   The proportion of the esters in the mixture as a whole is        preferably at least 10% by weight, in particular ≧30% by weight.    -   Of the compounds E-1 to E-3, the compound E-1 is particularly        preferred.

-   r) Liquid-crystalline medium additionally comprising one or more    tolans of the formulae To-1 and To-2

-   -   in which R and alkyl have the above-mentioned meanings.    -   The proportion of the tolans To-1 and/or To-2 in the mixture as        a whole is preferably at least 5% by weight, in particular 20%        by weight.    -   In the compounds To-1 and To-2, R preferably denotes        straight-chain alkyl or alkoxy.

-   s) Liquid-crystalline medium additionally comprising one or more    nitrites of the formulae N-1 and N-2

-   -   in which R and alkyl have the above-mentioned meanings.    -   The proportion of the nitriles in the mixture as a whole is        preferably at least 5% by weight, in particular 25% by weight.

-   t) Liquid-crystalline medium comprising at least 10% by weight,    preferably ≧15% by weight, in particular ≧20% by weight, of    compounds of the formula B-4. Compounds of this type are preferably    used in mixtures having a Δn≧0.12. The biphenyls of the formula B-4    are preferably employed in combination with compounds of the    formulae II and/or B-1.    -   Preferred mixtures having a Δn≧0.12 comprise at least 15% by        weight of compounds of the formula II and/or ≧5% by weight of        compounds of the formula B-1 besides the compounds of the        formula B-4.    -   Compounds of the formula B-4 are furthermore preferably employed        in combination with terphenyls, preferably with T-1, T-2 and/or        T-3.

-   u) Liquid-crystalline medium comprising at least one compound of the    formulae Z-1 to Z-10

-   -   in which R and alkyl have the above-mentioned meanings, and p is        1 or 2,    -   preferably in amounts of 5% by weight, in particular 10% by        weight.    -   Particular preference is given to media which comprise one, two        or more compounds of the formulae Z-1 to Z-7 and additionally        one, two or more compounds of the formula II. Mixtures of this        type preferably comprise ≧10% by weight of compounds of the        formula II and optionally also compounds of the formula IA.

-   v) Liquid-crystalline medium comprising at least one compound of the    formula

-   -   Preferred compounds of the formula IB-M are the compounds IB-M1        to IB-M3:

-   -   The mixtures according to the invention preferably comprise at        least one compound of the formula IB-M, in particular the        compound IB-M1, IB-M2 and/or IB-M3, and at least one compound

-   w) Liquid-crystalline medium comprising at least one compound of the    formulae

-   -   and/or

-   -   preferably in amounts of 5-20% by weight, in particular in        combination with one or more compounds of the formulae T-1 to        T-21.

-   x) Liquid-crystalline medium comprising at least one compound of the    formula T-1 and at least one compound of the formula T-4.

-   y) Liquid-crystalline medium comprising at least one compound of the    formula

-   -   and at least one compound of the formula

The invention furthermore relates to an electro-optical display havingactive-matrix addressing based on the ECB effect, characterised in thatit contains, as dielectric, a liquid-crystalline medium according to oneof Claims 1 to 17.

The liquid-crystal mixture preferably has a nematic phase range of atleast 60 K and a flow viscosity ν₂₀ of at most 30 mm²·s⁻¹, preferably<25 mm²·s⁻¹, at 20° C.

The liquid-crystal mixture according to the invention has a Δ∈ of about−2.3 to −8.0, in particular about −3.0 to −6.0, very particularlypreferably ≦−3.0 to −5.0.

The rotational viscosity γ₁ is preferably <200 mPa·s, in particular <190mPa·s.

-   z) Liquid-crystalline medium comprising at least one compound of the    formulae O-1 to O-11

-   -   in which R¹ and R² have the above-mentioned meanings, R¹ and R²        preferably each, independently of one another, denote        straight-chain alkyl, furthermore alkenyl.    -   Preferred liquid-crystalline media according to the invention        comprise one or more substances having a Δ∈<2.3 which contain a        tetrahydronaphthyl or naphthyl unit, such as, for example, the        compounds of the formulae N-1 to N-5

-   -   in which R¹ and R² each, independently of one another, have the        above-mentioned meanings, preferably denote straight-chain        alkyl, straight-chain alkoxy or straight-chain alkenyl, and Z,        Z¹ and Z² each, independently of one another, denote —C₂H₄—,        —CH═CH—, —(CH₂)₄—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CHCH₂CH₂—,        —CH₂CH₂CH═CH—, —CH₂O—, —OCH₂—, —COO—, —OCO—, —CF═CF—, —CF═CH—,        —CH═CF—, —CH₂— or a single bond.

The birefringence Δn in the liquid-crystal mixture is, generally,between 0.07 and 0.16, preferably between 0.08 and 0.12.

The mixtures according to the invention are suitable for all VA-TFTapplications, such as, for example, VAN, MVA, (S)-PVA, ASV. They arefurthermore suitable for IPS (in plane switching) and FFS (fringe fieldswitching) LCD applications having negative Δ∈.

The individual components of the formulae IA, IB, II and III of theliquid-crystal phases according to the invention are either known ortheir preparation methods can readily be derived from the prior art bythe relevant person skilled in the art since they are based on standardmethods described in the literature.

The nematic liquid-crystal mixtures in the displays according to theinvention generally comprise two components A and B, which themselvesconsist of one or more individual compounds.

Component A has clearly negative dielectric anisotropy and provides thenematic phase with a dielectric anisotropy of ≦−2.3. It preferablycomprises compounds of the formulae IA and/or IB and

The proportion of component A is preferably between 45 and 100%, inparticular between 60 and 100%.

For component A, one (or more) individual compound(s) having a value ofΔ∈≦−0.8 is (are) preferably selected. This value must be more negativethe smaller the proportion of A in the mixture as a whole.

Component B has pronounced nematogeneity and a flow viscosity of notgreater than 30 mm²·s⁻¹, preferably not greater than 25 mm²·s⁻¹, at 20°C.

Particularly preferred individual compounds of component B are extremelylow-viscosity nematic liquid crystals having a flow viscosity of notgreater than 18, preferably not greater than 12 mm²·s⁻¹, at 20° C.Component B is monotropically or enantiotropically nematic, has nosmectic phases and can prevent the occurrence of smectic phases inliquid-crystal mixtures down to very low temperatures. If, for example,various materials having high nematogeneity are each added to a smecticliquid-crystal mixture, the nematogeneity of these materials can becompared through the degree of suppression of smectic phases that isachieved. A multiplicity of suitable materials is known to the personskilled in the art from the literature. Particular preference is givento compounds of the formula III, furthermore compounds of the formulaeB-1 to B-4, O-1 and O-2.

In addition, these liquid-crystal phases may also comprise more than 18components, preferably 18 to 25 components.

The phases preferably comprise 4 to 15, in particular 5 to 12, compoundsof the formulae IA and/or IB, II and optionally III.

Besides compounds of the formulae IA and/or IB, II and III, otherconstituents may also be present, for example in an amount of up to 45%of the mixture as a whole, but preferably up to 35%, in particular up to10%.

The other constituents are preferably selected from nematic ornematogenic substances, in particular known substances, from the classesof the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenylor cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates,phenylcyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes,cyclehexylnaphthalenes, 1,4-biscyclohexylbiphenyls orcyclohexylpyrimidines, phenyl- or cyclohexyldioxanes, optionallyhalogenated stilbenes, benzyl phenyl ethers, tolans and substitutedcinnamic acids.

The most important compounds which are suitable as constituents ofliquid-crystal phases of this type can be characterised by the formulaIV

R⁹-L-G-E-R¹⁰  IV

in which L and E each denote a carbocyclic or heterocyclic ring systemfrom the group formed by 1,4-disubstituted benzene and cyclohexanerings, 4,4′-disubstituted biphenyl, phenylcyclohexane andcyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and1,3-dioxane rings, 2,6-disubstituted naphthalene, di- andtetrahydronaphthalene, quinazoline and tetrahydroquinazoline,

G denotes —CH═CH— —N(O)═N— —CH—CQ— —CH═N(O)— —C≡C— —CH₂—CH₂— —CO—O——CH₂—O— —CO—S— —CH₂—S— —CH═N— —COO-Phe-COO— —CF₂O— —CF═CF— —OCF₂ —OCH₂——(CH₂)₄— —(CH₂)₃O—or a C—C single bond, Q denotes halogen, preferably chlorine, or —CN,and R⁹ and R¹⁰ each denote alkyl, alkenyl, alkoxy, alkanoyloxy oralkoxycarbonyloxy having up to 18, preferably up to 8, carbon atoms, orone of these radicals alternatively denotes CN, NC, NO₂, NCS, SCN, CF₃,OCF₃, F, Cl or Br.

In most of these compounds, R⁹ and R¹⁰ are different from one another,one of these radicals usually being an alkyl or alkoxy group. Othervariants of the proposed substituents are also common. Many suchsubstances or also mixtures thereof are commercially available. Allthese substances can be prepared by methods known from the literature.

It goes without saying for the person skilled in the art that the VA,IPS, FFS or PA LCD mixture according to the invention may also comprisecompounds in which, for example, H, N, O, Cl and F have been replaced bythe corresponding isotopes.

The construction of the liquid-crystal displays according to theinvention corresponds to the usual geometry, as described, for example,in EP-A 0 240 379.

Besides the compounds of the formulae IA, IB, II and III, the mixturesaccording to the invention preferably comprise one or more of thecompounds mentioned above.

The following abbreviations are used:

The liquid-crystal mixtures which can be used in accordance with theinvention are prepared in a manner conventional per se. In general, thedesired amount of the components used in lesser amount is dissolved inthe components making up the principal constituent, advantageously atelevated temperature. It is also possible to mix solutions of thecomponents in an organic solvent, for example in acetone, chloroform ormethanol, and to remove the solvent again, for example by distillation,after thorough mixing.

In the present application, the term dielectrically positive compoundsdenotes compounds having a Δ∈>1.5, the term dielectrically neutralcompounds denotes those having −1.5≦Δ∈≦1.5 and the term dielectricallynegative compounds denotes those having Δ∈<−1.5. The dielectricanisotropy of the compounds is determined here by dissolving 10% of thecompounds in a liquid-crystalline host and determining the capacitanceof this mixture in at least one test cell in each case having a layerthickness of 20 μm with a homeotropic and with a homogeneous surfacealignment at 1 kHz. The measurement voltage is typically 0.5 V to 1.0 V,but is always lower than the capacitive threshold of the respectiveliquid-crystal mixture.

The host mixture used for dielectrically positive and dielectricallyneutral compounds is ZLI-4792 and that used for dielectrically negativecompounds is ZLI-2857, both from Merck KGaA, Germany. The values for therespective compounds to be investigated are obtained from the change inthe dielectric constants of the host mixture after addition of thecompound to be investigated and extrapolation to 100% of the compoundemployed.

The term threshold voltage relates in a conventional manner to theoptical threshold for 10% relative contrast (V₁₀), unless explicitlystated otherwise.

In the present application, however, the term threshold voltage is usedfor the capacitive threshold voltage (V₀), also known as the Freedericksthreshold, in relation to the liquid-crystal mixtures having negativedielectric anisotropy, unless explicitly stated otherwise.

All concentrations in this application, unless explicitly notedotherwise, are indicated in percent by weight and relate to thecorresponding mixture or mixture component. All physical properties aredetermined in accordance with “Merck Liquid Crystals, PhysicalProperties of Liquid Crystals”, Status November 1997, Merck KGaA,Germany, and apply for a temperature of 20° C., unless explicitly statedotherwise. An is determined at 589 nm and Δ∈ at 1 kHz.

For the liquid-crystal media having negative dielectric anisotropy, thethreshold voltage is determined as the capacitive threshold V₀ (alsoknown as the Freedericks threshold) in test cells produced at MerckKGaA, Germany, with liquid crystal homeotropically aligned by alignmentlayer SE 1211 from Nissan Chemicals.

The dielectrics may also comprise further additives known to the personskilled in the art and described in the literature, such as, forexample, UV absorbers, antioxidants, free-radical scavengers. Forexample, 0-15% of pleochroic dyes may be added, furthermore conductivesalts, preferably ethyldimethyldodecylammonium 4-hexyloxybenzoate,tetrabutylammonium tetraphenylborate or complex salts of crown ethers(cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. Volume 24,pages 249-258 (1973)), may be added in order to improve the conductivityor substances may be added in order to modify the dielectric anisotropy,the viscosity and/or the alignment of the nematic phases. Substances ofthis type are described, for example, in DE-A 22 09 127, 22 40 864, 2321 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

The liquid-crystal media according to the invention may, if necessary,also comprise chiral dopants in the conventional amounts. The amount ofthese dopants employed is in total 0 to 10%, based on the amount of themixture as a whole, preferably 0.1 to 6%. The concentration of theindividual compounds employed is preferably 0.1 to 3%. The concentrationof these and similar additives is not taken into account when indicatingthe concentrations and the concentration ranges of the liquid-crystalcompounds in the liquid-crystal media.

Table A indicates possible dopants which can be added to the mixturesaccording to the invention.

TABLE A

Stabilisers which can be added, for example, to the mixtures accordingto the invention in amounts of 0-10% are mentioned below in Table B.

TABLE B

(n = 1-12)

The compositions consist of a plurality of compounds, preferably of 3 to30, particularly preferably of 6 to 20 and very particularly preferablyof 10 to 16 compounds, which are mixed in a conventional manner. Ingeneral, the desired amount of the components used in lesser amount isdissolved in the components making up the principal constituent,advantageously at elevated temperature. If the selected temperature isabove the clearing point of the principal constituent, the completion ofthe dissolution process is particularly easy to observe. However, it isalso possible to prepare the liquid-crystal mixtures by otherconventional methods, for example using premixes or from a so-called“multibottle system”.

By means of suitable additives, the liquid-crystal phases according tothe invention can be modified in such a way that they can be employed inany type of ECB, VAN, IPS, GH or ASM-PA LCD display known to date.

The following examples serve to illustrate the invention withoutrestricting it. In the examples, the melting point T (C,N), thetransition from the smectic (S) to the nematic (N) phase T (S,N) andclearing point T (N,I) of a liquid-crystal substance are indicated indegrees Celsius.

Furthermore:

V_(o) denotes the threshold voltage, capacitive [V] at 20° C. Δn denotesthe optical anisotropy, measured at 20° C. and 589 nm Δ∈ denotes thedielectric anisotropy at 20° C. and 1 kHz cp. denotes clearing point [°C.] γ₁ denotes rotational viscosity, measured at 20° C. [mPa · s] LTSdenotes low-temperature stability, determined in test cells HR (20)denotes voltage holding ratio at 20° C. [%] HR (100) denotes voltageholding ratio after 5 min at 100° C. [%] HR (UV) denotes voltage holdingratio after UV exposure [%]

In order to measure the voltage holding ratio, cells with an AI-3046alignment layer are used.

The display for measurement of the threshold voltage has twoplane-parallel outer plates at a separation of 20 μm and electrodelayers with overlying SE-1211 (Nissan Chemicals) alignment layers on theinsides of the outer plates, which effect a homeotropic alignment of theliquid crystals.

USE EXAMPLES Example M1

CY-3-O4 16.00% Clearing point [° C.]: 71.0 CY-5-O2 13.00% Δn [589 nm,20° C.]: 0.0822 CCY-3-O2 14.00% ∈_(∥) [kHz, 20° C.]: 3.6 CCY-2-1 13.00%Δ∈ [kHz, 20° C.]: −3.3 CCY-3-1 10.00% K₁ [pN, 20° C.]: 13.3 CCH-3510.00% K₃ [pN, 20° C.]: 14.0 CCH-303 5.00% γ₁ [mPa · s, 20° C.]: 125CCH-301 12.00% V₀ [V]: 2.16 BCH-32 7.00% LTS: nematic >1000 h at −30° C.LTS:  nematic >350 h at −40° C. HR (100): 93.0%

Example M2

CY-3-O4 18.00% Clearing point [° C.]: 70.5 CY-5-O4 14.00% Δn [589 nm,20° C.]: 0.0825 CCY-3-O2 5.00% ∈_(∥) [kHz, 20° C.]: 3.4 CCY-5-O2 8.00%Δ∈ [kHz, 20° C.]: −3.1 CPY-2-O2 3.00% K₁ [pN, 20° C.]: 14.0 CPY-3-O210.00% K₃ [pN, 20° C.]: 14.4 CC-3-V1 12.00% γ₁ [mPa · s, 20° C.]: 102CC-5-V 15.00% V₀ [V]: 2.27 CC-3-2V 10.00% LTS: nematic >1000 h CCH-355.00% at −40° C. HR (100): 94.5%

Example M3

CY-3-O4 15.00% Clearing point [° C.]: 70.5 CY-5-O5 15.00% Δn [589 nm,20° C.]: 0.0952 CCY-3-O2 10.00% ∈_(∥) [kHz, 20° C.]: 3.5 CCY-3-1 10.00%Δ∈ [kHz, 20° C.]: −3.1 PCH-302 6.00% K₁ [pN, 20° C.]: 13.9 CC-5-V 6.00%K₃ [pN, 20° C.]: 14.6 CC-3-V1 12.00% γ₁ [mPa · s, 20° C.]: 133 CCH-355.00% V₀ [V]: 2.28 CPY-2-1 7.00% LTS: nematic >1000 h CPY-3-1 7.00% at−30° C. CPY-5-1 7.00%

Example M4

CY-3-O4 14.00% Clearing point [° C.]: 69.5 CY-5-O2 8.00% Δn [589 nm, 20°C.]: 0.1005 CY-5-O4 15.00% ∈_(∥) [kHz, 20° C.]: 3.6 BCH-32 8.00% Δ∈[kHz, 20° C.]: −3.3 CCP-V2-1 7.00% K₁ [pN, 20° C.]: 12.5 CC-3-V1 8.00%K₃ [pN, 20° C.]: 13.5 CC-3-V 18.00% γ₁ [mPa · s, 20° C.]: 106 CPY-2-O210.00% V₀ [V]: 2.14 CPY-3-O2 12.00% LTS: nematic >1000 h at −40° C.

Example M5

CY-3-O4 15.00% Clearing point [° C.]: 73.5 CY-5-O4 13.00% Δn [589 nm,20° C.]: 0.1198 PCH-53 5.00% ∈_(∥) [kHz, 20° C.]: 3.7 CCP-V-1 6.00% Δ∈[kHz, 20° C.]: −3.3 BCH-32 8.00% K₁ [pN, 20° C.]: 11.9 CC-3-V1 8.00% K₃[pN, 20° C.]: 12.0 CC-5-V 9.00% γ₁ [mPa · s, 20° C.]: 150 CPY-2-O212.00% V₀ [V]: 2.01 CPY-3-O2 12.00% YPY-4-1 6.00% YPY-4-4 6.00%

Example M6

CY-3-O4 11.00% Clearing point [° C.]: 71.0 CY-5-O2 11.00% Δn [589 nm,20° C.]: 0.1202 CPY-2-O2 12.00% ∈_(∥) [kHz, 20° C.]: 3.7 CPY-3-O2 9.00%Δ∈ [kHz, 20° C.]: −3.0 BCH-32 9.00% K₁ [20° C.]: 12.4 CCH-301 12.00% K₃[20° C.]: 11.7 CCH-303 12.00% γ₁ [mPa · s, 20° C.]: 125 CCH-35 6.00% V₀[V]: 2.10 PYP-2-3 6.00% LTS: nematic >1000 h PYP-2-4 12.00% at −30° C.

Example M7

CY-3-O4 20.00% Clearing point [° C.]: 70.0 CY-5-O4 5.00% Δn [589 nm, 20°C.]: 0.1201 CPY-2-O2 12.00% ∈_(∥) [kHz, 20° C.]: 3.6 CPY-3-O2 12.00% Δ∈[kHz, 20° C.]: −3.2 PYP-2-3 10.00% K₁ [20° C.]: 11.7 PYP-2-4 10.00% K₃[20° C.]: 12.4 CC-3-V1 12.00% γ₁ [mPa · s, 20° C.]: 116 CC-4-V 14.00% V₀[V]: 2.09 CCH-34 5.00%

Example M8

BCH-32 10.00% Clearing point [° C.]: 72.0 CCP-V-1 10.00% Δn [589 nm, 20°C.]: 0.1512 CC-3-V1 12.00% ∈_(∥) [kHz, 20° C.]: 3.7 CPY-2-O2 12.00% Δ∈[kHz, 20° C.]: −3.6 CPY-3-O2 13.00% K₁ [20° C.]: 15.0 B-302FF 19.00% K₃[20° C.]: 15.5 B-502FF 17.00% γ₁ [mPa · s, 20° C.]: 143 PP-1-4 7.00% V₀[V]: 2.20 LTS: nematic >1000 h at −30° C.

Example M9

CY-3-O2 18.00% Clearing point [° C.]: 71.0 CY-3-O4 5.00% Δn [589 nm, 20°C.]: 0.0821 CY-5-O2 12.00% ∈_(∥) [kHz, 20° C.]: 3.7 CCY-3-O2 12.00% Δ∈[kHz, 20° C.]: −3.9 CCY-5-O2 3.00% K₁ [20° C.]: 13.1 CCY-2-1 4.00% K₃[20° C.]: 14.9 CCY-3-1 8.00% γ₁ [mPa · s, 20° C.]: 130 CPY-3-O2 3.00% V₀[V]: 2.07 CCH-35 5.00% LTS: nematic >1000 h PCH-302 8.00% at −40° C.CH-33 3.00% HR (100° C.): 93% CH-43 4.00% CC-5-V 15.00%

Example M10

CY-3-O4 9.00% Clearing point [° C.]: 69.0 CY-5-O2 14.00% Δn [589 nm, 20°C.]: 0.0813 CY-5-O4 16.00% ∈_(∥) [kHz, 20° C.]: 3.7 CCY-3-O2 11.00% Δ∈[kHz, 20° C.]: −4.2 CCH-35 6.00% K₁ [20° C.]: 13.1 CC-3-V1 7.00% K₃ [20°C.]: 14.1 CC-5-V 18.00% γ₁ [mPa · s, 20° C.]: 116 CPY-3-O2 4.00% V₀ [V]:1.94 CCY-V-O2 15.00% LTS: nematic >1000 h at −30° C. LTS:  nematic >600h at −40° C. HR (100° C.): 94%

Example M11

CY-3-O4 17.00% Clearing point [° C.]: 70.5 CY-5-O2 9.00% Δn [589 nm, 20°C.]: 0.0993 CY-5-O4 14.00% ∈_(∥) [kHz, 20° C.]: 4.0 CPY-2-O2 7.00% Δ∈[kHz, 20° C.]: −4.2 CPY-3-O2 7.00% K₁ [20° C.]: 11.5 CCP-V-1 12.00% K₃[20° C.]: 14.3 CCH-35 5.00% γ₁ [mPa · s, 20° C.]: 187 CC-3-V1 9.00% V₀[V]: 1.95 CPQIY-3-O4 10.00% LTS: nematic >1000 h CPQIY-5-O4 10.00% at−30° C.

Example M12

CC-5-V 11.00% Clearing point [° C.]: 73.0 PCH-53 13.00% Δn [589 nm, 20°C.]: 0.0985 CY-3-O4 12.00% ε_(||) [kHz, 20° C.]: 3.7 CY-5-O4 12.00% Δε[kHz, 20° C.]: −4.0 CCY-2-O2 12.00% K₁ [20° C.]: 13.8 CCY-3-O2 12.00% K₃[20° C.]: 14.2 CCY-5-O2 8.00% γ₁ [mPa · s, 20° C.]: 163 CCY-2-1 10.00%V₀ [V]: 1.98 PYP-2-3 10.00%

Example M13

CY-3-O4 16.00% Clearing point [° C.]: 71.0 CY-5-O4 15.00% Δn [589 nm,20° C.]: 0.1014 CY-5-O2 8.00% ε_(||) [kHz, 20° C.]: 3.8 CCY-3-O2 6.00%Δε [kHz, 20° C.]: −4.0 BCH-32 7.00% K₁ [20° C.]: 13.9 CCH-35 5.00% K₃[20° C.]: 13.0 CC-3-2V 10.00% γ₁ [mPa · s, 20° C.]: 141 CC-5-V 9.00% V₀[V]: 1.89 CPY-2-O2 12.00% LTS: nematic >1000 h at CPY-3-O2 12.00% −30°C.

Example M14

CY-3-O4 20.00% Clearing point [° C.]: 73.5 CY-5-O2 9.00% Δn [589 nm, 20°C.]: 0.1202 CY-5-O4 4.00% ε_(||) [kHz, 20° C.]: 3.7 BCH-32 10.00% Δε[kHz, 20° C.]: −3.8 PGIGI-3-F 2.00% K₁ [20° C.]: 13.0 CC-3-V1 11.00% K₃[20° C.]: 13.1 CC-5-V 10.00% γ₁ [mPa · s, 20° C.]: 153 CPY-2-O2 14.00%V₀ [V]: 1.95 CPY-3-O2 12.00% LTS: nematic >1000 h at YPY-4-1 2.00% −20°C. YPY-4-4 2.00% YPY-5-5 2.00% YPY-4-2V 2.00%

Example M15

CY-3-O4 16.00% Clearing point [° C.]: 69.0 CY-5-O2 8.00% Δn [589 nm, 20°C.]: 0.1249 CY-5-O4 16.00% ε_(||) [kHz, 20° C.]: 3.9 BCH-32 8.00% Δε[kHz, 20° C.]: −4.1 CC-5-V 8.00% K₁ [20° C.]: 12.7 CC-3-V1 8.00% K₃ [20°C.]: 13.1 CPY-2-O2 11.00% γ₁ [mPa · s, 20° C.]: 153 CPY-3-O2 11.00% V₀[V]: 1.89 PYP-2-3 14.00% LTS: nematic >1000 h at −40° C.

Example M16

CY-3-O4 20.00% Clearing point [° C.]: 71.0 CY-5-O2 8.00% Δn [589 nm, 20°C.]: 0.1210 CY-5-O4 12.00% ε_(||) [kHz, 20° C.]: 4.0 BCH-32 9.00% Δε[kHz, 20° C.]: −4.1 CCP-V-1 7.00% K₁ [20° C.]: 12.4 PGIGI-3-F 7.00% K₃[20° C.]: 13.8 CC-3-V1 8.00% γ₁ [mPa · s, 20° C.]: 171 PCH-53 3.00% V₀[V]: 1.94 CPY-2-O2 14.00% LTS: nematic >1000 h at CPY-3-O2 12.00% −30°C. LTS: nematic >600 h at −40° C.

Example M17

CY-3-O4 16.00% Clearing point [° C.]: 68.5 CY-5-O2 8.00% Δn [589 nm, 20°C.]: 0.1515 BCH-32 8.00% ε_(||) [kHz, 20° C.]: 4.2 CC-3-V1 10.00% Δε[kHz, 20° C.]: −4.0 CPY-2-O2 12.00% K₁ [20° C.]: 13.0 CPY-3-O2 12.00% K₃[20° C.]: 14.4 PYP-2-3 11.00% γ₁ [mPa · s, 20° C.]: 161 PYP-3-3 10.00%V₀ [V]: 2.01 B-11FF 13.00% LTS: nematic >1000 h at −40° C.

Example M18

CC-5-V 7.00% Clearing point [° C.]: 70.0 CCH-34 6.00% Δn [589 nm, 20°C.]: 0.0796 CY-3-O4 22.00% ε_(||) [kHz, 20° C.]: 4.0 CY-5-O4 21.00% Δε[kHz, 20° C.]: −4.8 CCY-2-O2 8.00% K₁ [20° C.]: 12.9 CCY-3-O2 6.00% K₃[20° C.]: 12.6 CCY-5-O2 7.00% γ₁ [mPa · s, 20° C.]: 172 CCY-2-1 10.00%V₀ [V]: 1.72 CCY-3-1 8.00% LTS: nematic >1000 h at CH-33 2.00% −40° C.CH-43 3.00%

Example M19

CC-5-V 13.00% Clearing point [° C.]: 73.0 CY-3-O4 20.00% Δn [589 nm, 20°C.]: 0.0830 CY-5-O4 20.00% ε_(||) [kHz, 20° C.]: 3.9 CCY-2-O2 8.00% Δε[kHz, 20° C.]: −5.1 CCY-3-O2 11.00% K₁ [20° C.]: 13.2 CCY-5-O2 8.00% K₃[20° C.]: 14.0 CCY-2-1 10.00% γ₁ [mPa · s, 20° C.]: 184 CCY-3-1 10.00%V₀ [V]: 1.76 LTS: nematic >1000 h at −20° C. LTS: nematic >800 h at −30°C.

Example M20

PCH-53 5.00% Clearing point [° C.]: 70.5 CY-3-O4 22.00% Δn [589 nm, 20°C.]: 0.0951 CY-5-O4 20.00% ε_(||) [kHz, 20° C.]: 4.1 CCY-2-O2 9.00% Δε[kHz, 20° C.]: −4.9 CCY-3-O2 10.00% K₁ [20° C.]: 12.9 CCY-5-O2 5.00% K₃[20° C.]: 13.2 CCY-2-1 12.00% γ₁ [mPa · s, 20° C.]: 210 CCY-3-1 8.00% V₀[V]: 1.73 BCH-32 4.00% LTS: nematic >1000 h at BCH-52 4.00% −40° C.PGIGI-3-F 1.00%

Example M21

CY-3-O4 16.00% Clearing point [° C.]: 70.0 CY-5-O2 16.00% Δn [589 nm,20° C.]: 0.1019 CY-5-O4 13.00% ε_(||) [kHz, 20° C.]: 4.0 CCY-3-O2 9.00%Δε [kHz, 20° C.]: −5.0 CPY-2-O2 12.00% K₁ [20° C.]: 13.8 CPY-3-O2 12.00%K₃ [20° C.]: 14.5 CC-3-V1 10.00% γ₁ [mPa · s, 20° C.]: 165 CCH-35 9.00%V₀ [V]: 1.79 BCH-32 3.00%

Example M22

CCY-3-O2 15.00% Clearing point [° C.]: 87.0 CCY-5-O2 12.00% Δn [589 nm,20° C.]: 0.0797 CCY-2-1 6.00% ε_(||) [kHz, 20° C.]: 3.2 CCY-3-1 13.00%Δε [kHz, 20° C.]: −3.1 CY-5-O2 17.00% K₁ [20° C.]: 17.0 CCH-301 7.00% K₃[20° C.]: 17.8 CCH-35 20.00% γ₁ [mPa · s, 20° C.]: 147 PCH-53 10.00% V₀[V]: 2.53

Example M23

BCH-32F 2.50% Clearing point [° C.]: 92.0 CCH-301 16.50% Δn [589 nm, 20°C.]: 0.0827 CCH-34 5.00% ε_(||) [kHz, 20° C.]: 3.4 CCH-35 5.00% Δε [kHz,20° C.]: −3.0 CCY-2-1 14.00% K₁ [20° C.]: 16.4 CCY-3-O2 13.50% K₃ [20°C.]: 17.8 CCY-3-1 14.00% γ₁ [mPa · s, 20° C.]: 154 CCY-5-O2 13.50% V₀[V]: 2.58 PCH-301 8.50% CY-3-O2 7.50%

Example M24

CY-3-O4 8.00% Clearing point [° C.]: 91.0 CY-5-O2 3.00% Δn [589 nm, 20°C.]: 0.0822 CCY-3-O2 11.00% ε_(||) [kHz, 20° C.]: 3.3 CCY-3-O3 12.00% Δε[kHz, 20° C.]: −3.2 CCY-4-O2 12.00% K₁ [20° C.]: 15.4 CPY-2-O2 10.00% K₃[20° C.]: 15.9 CC-4-V 17.00% γ₁ [mPa · s, 20° C.]: 117 CC-3-V1 12.00% V₀[V]: 2.36 CCH-35 4.00% LTS: nematic >1000 h at CCH-301 11.00% −20° C.

Example M25

CY-3-O4 12.00% Clearing point [° C.]: 90.0 CCY-3-O3 12.00% Δn [589 nm,20° C.]: 0.1019 CCY-4-O2 2.00% ε_(||) [kHz, 20° C.]: 3.4 CPY-2-O2 12.00%Δε [kHz, 20° C.]: −3.0 CPY-3-O2 12.00% K₁ [20° C.]: 15.2 CCH-301 11.00%K₃ [20° C.]: 15.8 CC-5-V 20.00% γ₁ [mPa · s, 20° C.]: 135 CC-3-V1 10.00%V₀ [V]: 2.43 PYP-2-3 2.00% PYP-2-4 4.00% CCPC-33 3.00%

Example M26

CY-3-O4 15.00% Clearing point [° C.]: 90.5 CY-5-O4 11.00% Δn [589 nm,20° C.]: 0.1249 CY-5-O2 5.00% ε_(||) [kHz, 20° C.]: 3.7 CPY-2-O2 12.00%Δε [kHz, 20° C.]: −3.3 CPY-3-O2 12.00% K₁ [20° C.]: 15.2 BCH-32 8.00% K₃[20° C.]: 15.6 PGIGI-3-F 8.00% γ₁ [mPa · s, 20° C.]: 188 CCP-V-1 8.00%V₀ [V]: 2.38 CCP-V2-1 8.00% LTS: nematic >1000 h at CC-5-V 9.00% −30° C.CC-3-V1 2.00% HR (100° C.): 94% CBC-33 2.00%

Example M27

CY-3-O2 12.00% Clearing point [° C.]: 91.0 CY-5-O2 11.00% Δn [589 nm,20° C.]: 0.0829 CCY-3-O2 14.00% ε_(||) [kHz, 20° C.]: 3.6 CCY-5-O215.00% Δε [kHz, 20° C.]: −4.2 CCY-2-1 10.00% K₁ [20° C.]: 16.6 CCY-3-114.00% K₃ [20° C.]: 18.4 CCH-34 6.00% γ₁ [mPa · s, 20° C.]: 185 CCH-355.00% CCH-301 4.00% CCH-303 5.00% CCH-501 4.00%

Example M28

CY-3-O2 20.00% Clearing point [° C.]: 91.0 CY-5-O2 5.00% Δn [589 nm, 20°C.]: 0.0821 CCY-3-O2 12.00% ε_(||) [kHz, 20° C.]: 3.5 CCY-5-O2 7.00% Δε[kHz, 20° C.]: −4.1 CCY-3-O3 12.00% K₁ [20° C.]: 16.2 CCY-4-O2 11.00% K₃[20° C.]: 18.1 CC-5-V 20.00% γ₁ [mPa · s, 20° C.]: 148 CC-3-V1 9.00% V₀[V]: 2.21 CCH-35 4.00% LTS: nematic >1000 h at −20° C.

Example M29

CY-5-O2 9.00% Clearing point [° C.]: 90.5 CY-5-O4 15.00% Δn [589 nm, 20°C.]: 0.1023 CCY-3-O3 12.00% ε_(||) [kHz, 20° C.]: 3.5 CCY-4-O2 10.00% Δε[kHz, 20° C.]: −4.1 CCY-5-O2 10.00% K₁ [20° C.]: 17.3 CPY-2-O2 2.00% K₃[20° C.]: 16.4 CPY-3-O2 12.00% γ₁ [mPa · s, 20° C.]: 211 CCH-35 7.00% V₀[V]: 2.10 CCH-303 4.00% LTS: nematic >1000 h at PCH-53 12.00% −20° C.BCH-32 7.00% HR (100° C.): 91%

Example M30

CY-3-O4 5.00% Clearing point [° C.]: 91.5 CY-5-O4 20.00% Δn [589 nm, 20°C.]: 0.1015 CCY-3-O3 12.00% ε_(||) [kHz, 20° C.]: 3.5 CCY-4-O2 10.00% Δε[kHz, 20° C.]: −4.2 CCY-5-O2 11.00% K₁ [20° C.]: 16.6 CPY-3-O2 10.00% K₃[20° C.]: 16.3 PYP-2-4 7.00% γ₁ [mPa · s, 20° C.]: 211 CC-3-V1 11.00% V₀[V]: 2.10 CC-5-V 11.00% LTS: nematic >1000 h at PCH-53 3.00% −20° C. HR(100° C.): 94%

Example M31

CY-3-O4 14.00% Clearing point [° C.]: 90.0 CY-5-O2 14.00% Δn [589 nm,20° C.]: 0.1168 CY-5-O4 4.00% ε_(||) [kHz, 20° C.]: 3.7 CCY-3-O2 6.00%Δε [kHz, 20° C.]: −4.2 CCY-5-O2 7.00% K₁ [20° C.]: 15.3 PGIG1-3-F 2.00%K₃ [20° C.]: 17.7 BCH-32 10.00% γ₁ [mPa · s, 20° C.]: 198 CPY-2-O210.00% V₀ [V]: 2.15 CPY-3-O2 14.00% CCP-V-1 2.00% CC-5-V 5.00% CC-3-V112.00%

Example M32

CY-3-O4 20.00% Clearing point [° C.]: 87.0 CY-5-O2 12.00% Δn [589 nm,20° C.]: 0.0808 CY-5-O4 20.00% ε_(||) [kHz, 20° C.]: 3.9 CCY-3-O2 7.00%Δε [kHz, 20° C.]: −5.0 CCY-5-O2 11.00% K₁ [20° C.]: 13.6 CCH-301 5.00%K₃ [20° C.]: 15.1 CH-33 4.00% γ₁ [mPa · s, 20° C.]: 265 CH-35 4.00% V₀[V]: 1.82 CH-43 4.00% CH-45 4.00% CCPC-33 3.00% CCPC-34 3.00% CCPC-353.00%

Example M33

CY-3-O4 14.00% Clearing point [° C.]: 86.0 CY-5-O2 10.00% Δn [589 nm,20° C.]: 0.1023 CY-5-O4 16.00% ε_(||) [kHz, 20° C.]: 3.9 CCY-2-O2 6.00%Δε [kHz, 20° C.]: −5.1 CCY-3-O2 12.00% K₁ [20° C.]: 15.2 CCY-5-O2 8.00%K₃ [20° C.]: 16.2 CCY-2-1 8.00% γ₁ [mPa · s, 20° C.]: 257 CCY-3-1 12.00%V₀ [V]: 1.89 BCH-32 8.00% LTS: nematic >1000 h at CCP-V-1 4.00% −20° C.PGIGI-3-F 2.00% LTS: nematic >760 h at −30° C. LTS: nematic >500 h at−40° C. HR (20° C.): 98% HR (100° C.): 91%

Example M34

CY-3-O4 10.00% Clearing point [° C.]: 90.0 CY-5-O4 14.00% Δn [589 nm,20° C.]: 0.1204 CY-5-O2 13.00% ε_(||) [kHz, 20° C.]: 3.9 CCY-3-O2 14.00%Δε [kHz, 20° C.]: −5.0 CCY-5-O2 1.00% K₁ [20° C.]: 14.7 CBC-33 6.00% K₃[20° C.]: 16.8 CC-5-V 11.00% γ₁ [mPa · s, 20° C.]: 265 PGIGI-3-F 7.00%V₀ [V]: 1.94 CPY-2-O2 12.00% LTS: nematic >1000 h at CPY-3-O2 12.00%−40° C.

Example M35

CY-3-O2 13.00% Clearing point [° C.]: 79.5 CY-5-O2 5.00% Δn [589 nm, 20°C.]: 0.0788 CCY-4-O2 10.00% ε_(||) [kHz, 20° C.]: 3.4 CCY-3-O3 12.00% Δε[kHz, 20° C.]: −3.1 CCY-2-O2V 11.00% K₁ [pN, 20° C.]: 13.9 CPY-2-O26.00% K₃ [pN, 20° C.]: 13.6 CCH-303 5.00% γ₁ [mPa · s, 20° C.]: 107CC-5-V 18.00% V₀ [V]: 2.21 CC-3-V1 12.00% CCH-34 5.00% PCH-301 3.00%

1. A liquid-crystalline medium based on a mixture of polar compoundshaving negative dielectric anisotropy (Δ∈), which has a value for theratio γ₁/Δn² in the range 6-45 Pa·s with a clearing point of >60° C. anda Δ∈ of −2.3, and comprises one or more compounds of formula PP-n-mPP-n-m

wherein n and m are each independently 1, 2, 3, 4, 5 or
 6. 2. Aliquid-crystalline medium according to claim 1, which has a Δ∈ clearingpoint of 60-90° C.
 3. A liquid-crystalline medium according to claim 1,which has a Δ∈ value of −2.3 to −5.5.
 4. A liquid-crystalline mediumaccording to claim 1, which having a clearing point of 70° C.±5° C. anda Δ∈ of −3.0±0.6 has the following rotational viscosities γ₁ at adefined Δn value: Δn γ₁ 0.08 ± 0.005 ≦125 mPa · s 0.09 ± 0.005 ≦130 mPa· s 0.10 ± 0.005 ≦135 mPa · s 0.11 ± 0.005 ≦145 mPa · s 0.12 ± 0.005≦150 mPa · s 0.13 ± 0.005 ≦160 mPa · s 0.15 ± 0.01 ≦170 mPa · s.


5. A liquid-crystalline medium according to claim 1, which having aclearing point of 70° C.±5° C. and a Δ∈ of >−3.6 and ≦−4.4 has thefollowing rotational viscosities γ₁ at a defined Δn value: Δn γ₁ 0.08 ±0.005 ≦140 mPa · s 0.09 ± 0.005 ≦165 mPa · s 0.10 ± 0.005 ≦185 mPa · s0.11 ± 0.005 ≦190 mPa · s 0.12 ± 0.005 ≦195 mPa · s 0.13 ± 0.005 ≦205mPa · s 0.15 ± 0.01 ≦220 mPa · s.


6. A liquid-crystalline medium according to claim 1, which having aclearing point of 70° C.±5° C. and a Δ∈ of >−4.4 and ≦−5.6 has thefollowing rotational viscosities γ₁ at a defined Δn value: Δn γ₁ 0.08 ±0.005 ≦185 mPa · s 0.09 ± 0.005 ≦200 mPa · s 0.10 ± 0.005 ≦210 mPa · s0.11 ± 0.005 ≦220 mPa · s 0.12 ± 0.005 ≦230 mPa · s 0.13 ± 0.005 ≦250mPa · s 0.15 ± 0.01 ≦270 mPa · s.


7. A liquid-crystalline medium according to claim 1, which having aclearing point of 90° C.±5° C. and a Δ∈ of −3.0±0.6 has the followingrotational viscosities γ₁ at a defined Δ∈ value: Δn γ₁ 0.08 ± 0.005 ≦160mPa · s 0.09 ± 0.005 ≦170 mPa · s 0.10 ± 0.005 ≦180 mPa · s 0.11 ± 0.005≦190 mPa · s 0.12 ± 0.005 ≦200 mPa · s 0.13 ± 0.005 ≦210 mPa · s 0.15 ±0.01 ≦220 mPa · s.


8. A liquid-crystalline medium according to claim 1, which having aclearing point of 90° C.±5° C. and a Δ∈ of >−3.6 and ≦−4.4 has thefollowing rotational viscosities γ₁ at a defined Δn value: Δn γ₁ 0.08 ±0.005 ≦185 mPa · s 0.09 ± 0.005 ≦195 mPa · s 0.10 ± 0.005 ≦215 mPa · s0.11 ± 0.005 ≦215 mPa · s 0.12 ± 0.005 ≦215 mPa · s 0.13 ± 0.005 ≦235mPa · s 0.15 ± 0.01 ≦250 mPa · s.


9. A liquid-crystalline medium according to claim 1, which having aclearing point of 90° C.±5° C. and a Δ∈ of >−4.4 and ≦−5.6 has thefollowing rotational viscosities γ₁ at a defined Δn value: Δn γ₁ 0.08 ±0.005 ≦280 mPa · s 0.09 ± 0.005 ≦275 mPa · s 0.10 ± 0.005 ≦275 mPa · s0.11 ± 0.005 ≦275 mPa · s 0.12 ± 0.005 ≦280 mPa · s.


10. A liquid-crystalline medium according to claim 1, which hasthresholds (capacitive) in the range 1.8-2.3 V.
 11. A liquid-crystallinemedium according to claim 1, which further comprises at least twocompounds of formulae IA, IB and/or II

in which R¹ and R² each, independently of one another, denote an alkylor alkenyl radical having up to 15 C atoms which is unsubstituted,monosubstituted by CN or CF₃ or at least monosubstituted by halogen, inwhich one or more CH₂ groups are optionally, independently of oneanother, replaced by —O—, —S—,

 —C≡C—, —CF₂O—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that Oatoms are not linked directly to one another, and v denotes 1 to
 6. 12.A liquid-crystalline medium according to claim 1, which additionallycomprises one or more compounds of the formula III

in which R³¹ and R³² each, independently of one another, denote astraight-chain alkyl, alkylalkoxy or alkoxy radical having up to 12 Catoms, and

 denotes

 and Z denotes a single bond, —C₂H₄—, —CH═CH—, —(CH₂)₄—, —(CH₂)₃O—,—O(CH₂)₃—, —CH═CHCH₂CH₂—, —CH₂CH₂CH═CH—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—,—COO—, —OCO—, —C₂F₄—, —CHFCF₂—, —CF═CF—, —CH═CF—, —CF═CH—, or —CH₂—. 13.A liquid-crystalline medium according to claim 11, which comprises one,two, three, four, five or six compounds of the formulae IA, IB and/orII.
 14. A liquid-crystalline medium according to claim 11, wherein theproportion of compounds of the formulae IA and/or IB in the mixture as awhole is at least 10% by weight.
 15. A liquid-crystalline mediumaccording to claim 11, wherein the proportion of compounds of theformula II in the mixture as a whole is at least 10% by weight.
 16. Aliquid-crystalline medium according to claim 12, wherein the proportionof compounds of the formula III in the mixture as a whole is at least 5%by weight.
 17. A liquid-crystalline medium according to claim 11, whichessentially consists of 10-40% by weight of one or more compounds of theformulae IA and IB and 10-40% by weight of one or more compounds of theformula II.
 18. An electro-optical display having active-matrixaddressing based on the ECB, PA LCD, FFS or the IPS effect, whichcontains, as dielectric, a liquid-crystalline medium according toclaim
 1. 19. A liquid-crystalline medium according to claim 1, whichcontains as a compound of formula PP-n-m a compound of the followingformula

wherein alkyl* denotes a straight-chain alkyl radical having 1-6 Catoms.
 20. A liquid-crystalline medium according to claim 1, whichcontains as a compound of formula PP-n-m wherein n is 1 and m is 4.